Chromogenic absorbent material for animal litter

ABSTRACT

A chromogenic absorbent material for an animal litter includes an oxidizing agent responsive to peroxidatic/pseudoperoxidatic activity in an animal excretion or a first catalytic compound generating the oxidizing agent in situ. The material also includes a chromogenic indicator being chromogenically responsive to the oxidizing activity of the oxidizing agent, and an absorptive material which is porous, for absorbing the animal excretion. The absorptive material includes a water-absorbing polysaccharide providing absorptive properties to the chromogenic absorbent material; and may also include a second polysaccharide and a superabsorbent polymer. The material may be obtained in the form of particles having a low density and a high porosity, and is usable in conjunction with an animal litter for detecting various diseases in animals.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/121,936, filed on Aug. 26, 2016, which is a National Stageapplication of International Application No. PCT/CA2014/050140, filedFeb. 27, 2014, each of which is incorporated by reference herein intheir entirety.

FIELD

The technical field relates to animal disease detection and chromogenicmaterials, and more particularly to animal litter including chromogenicabsorbent material for detecting animal diseases.

BACKGROUND

Domestic animals such as cats are susceptible to various diseases,ailments and conditions, which are not only arduous and painful for theanimal itself but also a source of concern and stress for animal owners.While animal owners nurture, watch over and bestow affection on theirpets, they must balance this attention with other responsibilities.Convenience is thus an important factor when taking care of a domesticanimal. While owners may be devoted and considerate to their pets, theymay lack the sophistication to diagnose animal diseases, ailments andconditions. Convenient, simple and effective means to inform pet ownersof the presence of diseases, such as urinary infections, are desired sothat appropriate steps can be taken to reverse, mitigate or avoidserious illness in the animal.

For example, feline urinary tract disease can be a serious condition forcats. In feline urinary tract disease, crystals of magnesium ammoniumphosphate can precipitate in the cat's urinary tract and causeobstruction. If untreated, the obstruction can lead to intense pain andcan often be fatal within days. In some cases, upon observing felineurinary tract disease symptoms—such as bloody urine and urinationdiscomfort and straining—cat owners often consult their veterinarian whomay be able to provide treatments, which may be expensive. However, manycats with feline urinary tract disease do not show any obvious symptoms,which is why this disease has been referred to as a “silent killer”.

Another example of a serious condition for cats is diabetes. Diabetesstrikes about 1 in 400 cats and has become increasingly common. Symptomsof diabetes in cats are similar to those in humans, and about 80% to 95%of diabetic cats experience something similar to type-2 diabetes inhumans. Cats suffering of diabetes usually become severelyinsulin-dependent by the time symptoms are diagnosed. In cats sufferingfrom type-2 diabetes, early treatment can sometimes lead to diabeticremission, in which the cat no longer needs injected insulin. If leftuntreated, the condition leads to increasingly weak cats, malnutrition,ketoacidosis and/or dehydration, and eventually death.

Early detection of diseases such as feline urinary tract disease ordiabetes is therefore of paramount importance in facilitating treatment,lessening the likelihood of severe complications or aggravations, andreducing the cost of treatment.

Some methods of early detection are known. Early detection may bepossible by occult blood testing, allowing animal owners to treat theproblems of urinary tract disease or diabetes by changing the animals'diets or by seeking the help of a veterinarian. However, some knownoccult blood or glucose testing techniques present various disadvantagesconcerning the complexity and inconvenience of the tests. For instance,animals will often resist urine sample gathering.

It is known to use diagnostic agents, incorporated into test strips,beads or particles, for detection purposes. Usually, such test stripsconsist of an absorbent carrier made from fibrous or non-woven material,in the simplest case filter paper, which is coated or impregnated withthe detection reagents. Components of the detection reagent may be achromogenic compound as an indicator, an oxidizing agent such as ahydroperoxide as an oxidizer of the indicator. The oxidizing agent issometimes also called a sensitizer or an accelerator. Standardadditional components are, apart from a surface-active agent (wettingagent), thickening agents which prevent the bleeding of the wetted testfield, pigments, complex-forming agents and/or other stabilizers for thechromogen and/or the hydroperoxide.

Similarly, various analytical methods are presently available fordetecting the presence of “peroxidatively active substances” in samplessuch as urine, fecal suspensions, and gastrointestinal contents.According to U.S. Pat. No. 4,460,684, hemoglobin and its derivatives aretypical of such peroxidatively active substances because they behave ina manner similar to the enzyme peroxidase. Such substances are alsoreferred to as pseudoperoxidases. Peroxidatively active substances areenzyme-like in that they catalyze the redox reaction between peroxidesand benzidine, o-tolidine, 3,3′,5,5′-tetramethylbenzidine,2,7-diaminofluorene or similar benzidine-type indicator substances,thereby producing a detectable response such as a color change. Forexample, most methods for determining the presence of occult blood intest samples rely on this pseudoperoxidatic activity. A benzidine-typeindicator responds in the presence of hydroperoxide and/or peroxidase bychanging its light absorptive capability.

Providing a reliable occult blood or glucose detection system in animallitter itself also has many problems and challenges. For example, thetest indicator material should be stable when exposed to a wide varietyof ambient conditions, be they dry or humid, and over a wide range oftemperatures. Such stability is quite often difficult to achieve.

A further problem with many known test indicators is that pet owners areinsufficiently observant or sophisticated to appreciate the positiveindication, such as a color change, before the indicator decays. Manyknown indicators do not stay at the changed color for a sufficientperiod of time to allow pet owners to reliably recognize the indicatedhealth issue.

An additional problem with various detection reagents mixed with animallitter is that the test reagents give off sufficient scent such thatcats, which have an extraordinary sense of smell, recognize the odorchange in their litter and thus tend to shy away from the litter. Aswill be appreciated, this not only defeats the purpose of a convenientdetector but can also cause unwanted excretory mishaps. Thus, testreagents with significant, offensive or upsetting odors—both to the userand the cat—have many disadvantages.

A further problem with known detection reagents is poor shelf lifestability, particularly if combined with an animal litter for storage asa single mixture. Poor stability leads to disadvantages in the abilityto store, transport, display, purchase and use the detection-littercombination.

Detection materials that are merely coated over the surface of a carriermaterial also have various disadvantages that may relate to poorshelf-life stability, low in-use stability and lifetime, andinsufficient color change visibility.

Known materials and methods for detection of feline urinary tractdisease or diabetes have involved one or more of the above deficiencies.

Some detection methods are disclosed in WO 2010133001 (Jollez et al.)which describes a chromogenic composite material for use with animallitter. The composite material can include an absorptive polymermaterial; clay; a chromogenic indicator; and an oxidizing agent that isavailable and responsive to peroxidase or pseudoperoxidase activity inthe feline urine to activate the chromogenic indicator. The chromogenicindicator may be 3,3′,5,5′-tetramethylbenzidine, also referred to asTMB.

Despite the developments in detection methods for animal excretion tractdisease, there is still a need for an improved technology.

SUMMARY

A chromogenic absorbent material is described herein for detectingsubstances in animal excretions.

In some implementations, there is provided a chromogenic absorbentmaterial for an animal litter, comprising:

-   -   an oxidizing agent responsive to peroxidatic/pseudoperoxidatic        activity in an animal excretion to provide oxidizing activity;    -   a chromogenic indicator being chromogenically responsive to the        oxidizing activity of the oxidizing agent; and    -   an absorptive material which is porous, for absorbing the animal        excretion, the absorptive material comprising:        -   a water-absorbing polysaccharide providing absorptive            properties to the chromogenic absorbent material; and        -   a second polysaccharide providing structural integrity to            the chromogenic absorbent material.

In some implementations, the second polysaccharide comprises acrystalline polysaccharide.

In some implementations, the crystalline polysaccharide comprisescellulose, a cellulose derivative or mixtures thereof.

In some implementations, the cellulose comprises microcrystallinecellulose (MCC), nanocrystalline cellulose (NCC), or a mixture thereof.

In some implementations, the absorptive material comprises:

-   -   about 35 wt. % to about 65 wt. % of the water-absorbing        polysaccharide; and    -   about 35 wt. % to about 65 wt. % of the second polysaccharide.

In some implementations, the absorptive material comprises:

-   -   about 45 wt. % to about 55 wt. % of the water-absorbing        polysaccharide; and    -   about 45 wt. % to about 55 wt. % of the second polysaccharide.

In some implementations, there is provided a chromogenic absorbentmaterial for an animal litter, comprising:

-   -   an oxidizing agent responsive to peroxidatic/pseudoperoxidatic        activity in an animal excretion to provide oxidizing activity;    -   a chromogenic indicator being chromogenically responsive to the        oxidizing activity of the oxidizing agent; and    -   an absorptive material which is porous, for absorbing the animal        excretion, the absorptive material comprising a water-absorbing        polysaccharide,    -   wherein the chromogenic absorbent material has a density of        about 0.20 g/cm³ to about 0.39 g/cm³.

In some implementations, the density of the chromogenic absorbentmaterial is about 0.25 g/cm³ to about 0.35 g/cm³.

In some implementations, the density of the chromogenic absorbentmaterial is about 0.30 g/cm³ to about 0.35 g/cm³.

In some implementations, there is provided a chromogenic absorbentmaterial for an animal litter, comprising:

-   -   an oxidizing agent responsive to peroxidatic/pseudoperoxidatic        activity in an animal excretion to provide oxidizing activity;    -   a chromogenic indicator being chromogenically responsive to the        oxidizing activity of the oxidizing agent; and    -   an absorptive material which is porous, for absorbing the animal        excretion, the absorptive material comprising a water-absorbing        polysaccharide,    -   wherein the chromogenic absorbent material is a porous material        having an effective porosity of about 0.5 mL/g to about 2.0        mL/g.

In some implementations, the effective porosity is of about 0.6 mL/g toabout 1.5 mL/g.

In some implementations, the effective porosity is of about 0.8 mL/g toabout 1.2 mL/g.

In some implementations, the effective porosity is of about 0.9 mL/g toabout 1.1 mL/g.

In some implementations, the chromogenic absorbent material is providedwith pores having an equivalent diameter greater than about 20 μm.

In some implementations, the chromogenic absorbent material is providedwith pores having an equivalent diameter of about 20 μm to about 40 μm.

In some implementations, the chromogenic absorbent material is providedwith pores having an equivalent diameter of about 20 μm to about 30 μm.

In some implementations, the chromogenic absorbent material has a freeswelling capacity greater than about 900%.

In some implementations, the chromogenic absorbent material has a freeswelling capacity greater than about 1000%.

In some implementations, there is provided a chromogenic absorbentmaterial for an animal litter, comprising:

-   -   an oxidizing agent responsive to peroxidatic/pseudoperoxidatic        activity in an animal excretion to provide oxidizing activity;    -   a chromogenic indicator being chromogenically responsive to the        oxidizing activity of the oxidizing agent; and    -   an absorptive material which is porous, for absorbing the animal        excretion, the absorptive material comprising:        -   a water-absorbing polysaccharide providing absorptive            properties to the chromogenic absorbent material; and        -   a superabsorbent polymer (SAP).

In some implementations, the absorptive material comprises up to about 3wt. % of the SAP.

In some implementations, the absorptive material comprises about 1 wt. %to about 3 wt. % of the SAP.

In some implementations, the absorptive material comprises about 1 wt. %to about 2 wt. % of the SAP.

In some implementations, the SAP comprises at least one of apoly(acrylic acid) and a poly(methacrylic acid), or a salt thereof.

In some implementations, there is provided a chromogenic absorbentmaterial for an animal litter, comprising:

-   -   an oxidizing agent responsive to peroxidatic/pseudoperoxidatic        activity in an animal excretion to provide oxidizing activity;    -   a chromogenic indicator being chromogenically responsive to the        oxidizing activity of the oxidizing agent; and    -   an absorptive material which is porous, for absorbing the animal        excretion, the absorptive material comprising:        -   a water-absorbing polysaccharide providing absorptive            properties to the chromogenic absorbent material; and        -   a second polysaccharide providing structural integrity to            the chromogenic absorbent material,    -   wherein the chromogenic absorbent material is a porous material        having:        -   an effective porosity of about 0.5 mL/g to about 2.0 mL/g;            and        -   a density of about 0.20 g/cm³ to about 0.39 g/cm³.

In some implementations, the water-absorbing polysaccharide comprises astarch, a modified starch, a cellulose derivative or a gellingpolysaccharide, or a mixture thereof.

In some implementations, the water-absorbing polysaccharide comprisespregelatinized starch.

In some implementations, the cellulose derivative comprises a celluloseester or a cellulose ether, or a mixture thereof.

In some implementations, the cellulose derivative comprisescarboxymethyl cellulose (CMC).

In some implementations, the gelling polysaccharide comprises agar-agar,guar or xanthan, or a mixture thereof.

In some implementations, the oxidizing agent comprises a hydroperoxideor a hydroperoxide precursor, or a combination thereof.

In some implementations, the hydroperoxide comprises hydrogen peroxide,cumene hydroperoxide or diisopropylbenzene dihydroperoxide, or acombination thereof.

In some implementations, the oxidizing agent and the chromogenicindicator are distributed within the absorptive material.

In some implementations, the chromogenic indicator comprises abenzidine-type compound.

In some implementations, the benzidine-type compound comprises3,3′,5,5′-tetramethylbenzidine.

In some implementations, the chromogenic absorbent material furthercomprises a buffering agent, a stabilizer, a metal scavenger agent or acolor enhancer or a combination thereof.

In some implementations, the color enhancer comprises6-methoxyquinoline, lepidin, phenol derivatives, nitrobenzene,N-methylpyrrolidone or ethylene carbonate or a combination thereof.

In some implementations, the buffering agent comprises citrate, sodiumcitrate, phosphate or acetate or a combination thereof.

In some implementations, the stabilizer comprises ammonium molybdate,polyethylene glycol, polyvinylpyrrolidone, polyethylene oxide orderivatives thereof or a combination thereof.

In some implementations, the metal-scavenger agent comprisesethylenediaminetetraacetic acid (EDTA) or EDTA sodium salt or acombination thereof.

In some implementations, the chromogenic indicator is responsive to theoxidizing agent by turning blue in presence of theperoxidatic/pseudoperoxidatic activity in the animal excretions.

In some implementations, the chromogenic absorbent material turns toblue in presence of the peroxidatic/pseudoperoxidatic activity after acontact time with the animal excretion between about 10 seconds andabout 30 min.

In some implementations, the chromogenic absorbent material turns toblue in presence of the peroxidatic/pseudoperoxidatic activity after acontact time with the animal excretion between about 10 seconds andabout 1 min.

In some implementations, there is provided a chromogenic absorbentmaterial for an animal litter, comprising:

-   -   a first catalytic compound for in situ generation of an        oxidizing agent responsive to peroxidatic/pseudoperoxidatic        activity in an animal excretion, the oxidizing agent providing        oxidizing activity;    -   a chromogenic indicator being chromogenically responsive to the        oxidizing activity of the oxidizing agent;    -   a second catalytic compound for catalyzing the oxidation of the        chromogenic indicator upon in situ generation of the oxidizing        agent; and    -   an absorptive material which is porous, for absorbing the animal        excretion, the absorptive material comprising:        -   a water-absorbing polysaccharide providing absorptive            properties to the chromogenic absorbent material; and        -   a second polysaccharide providing structural integrity to            the chromogenic absorbent material.

In some implementations, there is provided a chromogenic absorbentmaterial for an animal litter, comprising:

-   -   a first catalytic compound for in situ generation of an        oxidizing agent responsive to peroxidatic/pseudoperoxidatic        activity in an animal excretion, the oxidizing agent providing        oxidizing activity;    -   a chromogenic indicator being chromogenically responsive to the        oxidizing activity of the oxidizing agent;    -   a second catalytic compound for catalyzing the oxidation of the        chromogenic indicator upon in situ generation of the oxidizing        agent; and    -   an absorptive material for absorbing the animal excretion, the        absorptive material comprising a water-absorbing polysaccharide,        wherein the chromogenic absorbent material has a density of        about 0.20 g/cm³ to about 0.39 g/cm³.

In some implementations, there is provided a chromogenic absorbentmaterial for an animal litter, comprising:

-   -   a first catalytic compound for in situ generation of an        oxidizing agent responsive to peroxidatic/pseudoperoxidatic        activity in an animal excretion, the oxidizing agent providing        oxidizing activity;    -   a chromogenic indicator being chromogenically responsive to the        oxidizing activity of the oxidizing agent;    -   a second catalytic compound for catalyzing the oxidation of the        chromogenic indicator upon in situ generation of the oxidizing        agent; and    -   an absorptive material for absorbing the animal excretion, the        absorptive material comprising a water-absorbing polysaccharide,    -   wherein the chromogenic absorbent material is a porous material        having an effective porosity of about 0.5 mL/g to about 2.0        mL/g.

In some implementations, there is provided a chromogenic absorbentmaterial for an animal litter, comprising:

-   -   a first catalytic compound for in situ generation of an        oxidizing agent responsive to peroxidatic/pseudoperoxidatic        activity in an animal excretion, the oxidizing agent providing        oxidizing activity;    -   a chromogenic indicator being chromogenically responsive to the        oxidizing activity of the oxidizing agent;    -   a second catalytic compound for catalyzing the oxidation of the        chromogenic indicator upon in situ generation of the oxidizing        agent; and    -   an absorptive material which is porous, for absorbing the animal        excretion, the absorptive material comprising:        -   a water-absorbing polysaccharide providing absorptive            properties to the chromogenic absorbent material; and        -   a superabsorbent polymer (SAP).

In some implementations, there is provided a chromogenic absorbentmaterial for an animal litter, comprising:

-   -   a first catalytic compound for in situ generation of an        oxidizing agent responsive to peroxidatic/pseudoperoxidatic        activity in an animal excretion, the oxidizing agent providing        oxidizing activity;    -   a chromogenic indicator being chromogenically responsive to the        oxidizing activity of the oxidizing agent;    -   a second catalytic compound for catalyzing the oxidation of the        chromogenic indicator upon in situ generation of the oxidizing        agent; and    -   an absorptive material which is porous, for absorbing the animal        excretion, the absorptive material comprising:        -   a water-absorbing polysaccharide providing absorptive            properties to the chromogenic absorbent material; and        -   a second polysaccharide providing structural integrity to            the chromogenic absorbent material,    -   wherein the chromogenic absorbent material is a porous material        having:        -   an effective porosity of about 0.5 mL/g to about 2.0 mL/g;            and        -   a density of about 0.20 g/cm³ to about 0.39 g/cm³.

In some implementations, the water-absorbing polysaccharide comprises acellulose derivative or a gelling polysaccharide, or a mixture thereof.

In some implementations, the first catalytic compound comprises anoxido-reductase enzyme.

In some implementations, the oxido-reductase comprises glucose oxidase(GOx).

In some implementations, the oxidizing agent generated in situ ishydrogen peroxide.

In some implementations, the second catalytic compound comprises aperoxidase, a pseudoperoxidase, or a mixture thereof.

In some implementations, the peroxidase comprises horseradish peroxidase(HRP).

In some implementations, the first catalytic compound, the secondcatalytic compound and the chromogenic indicator are distributed withinthe absorptive material.

In some implementations, there is provided a chromogenic absorbentmaterial for detecting a detectable substance in an animal excretion,the chromogenic absorbent material comprising:

-   -   a trigger agent;    -   a chromogenic indicator oxidizable into a colored and/or        fluorescent substance in the presence of the trigger agent and        the detectable substance; and    -   an absorptive material which is porous, for absorbing the animal        excretion, the absorptive material comprising:        -   a water-absorbing polysaccharide providing absorptive            properties to the chromogenic absorbent material; and        -   a second polysaccharide providing structural integrity to            the chromogenic absorbent material.

In some implementations, there is provided a chromogenic absorbentmaterial for detecting a detectable substance in an animal excretion,the chromogenic absorbent material comprising:

-   -   a trigger agent;    -   a chromogenic indicator oxidizable into a colored and/or        fluorescent substance in the presence of the trigger agent and        the detectable substance; and    -   an absorptive material which is porous, for absorbing the animal        excretion, the absorptive material comprising:        -   a water-absorbing polysaccharide providing absorptive            properties to the chromogenic absorbent material,    -   wherein the chromogenic absorbent material has a density of        about 0.20 g/cm³ to about 0.39 g/cm³.

In some implementations, there is provided a chromogenic absorbentmaterial for detecting a detectable substance in an animal excretion,the chromogenic absorbent material comprising:

-   -   a trigger agent;    -   a chromogenic indicator oxidizable into a colored and/or        fluorescent substance in the presence of the trigger agent and        the detectable substance; and    -   an absorptive material which is porous, for absorbing the animal        excretion, the absorptive material comprising:        -   a water-absorbing polysaccharide providing absorptive            properties to the chromogenic absorbent material, wherein            the chromogenic absorbent material is a porous material            having an effective porosity of about 0.5 mL/g to about 2.0            mL/g.

In some implementations, there is provided a chromogenic absorbentmaterial for detecting a detectable substance in an animal excretion,the chromogenic absorbent material comprising:

-   -   a trigger agent;    -   a chromogenic indicator oxidizable into a colored and/or        fluorescent substance in the presence of the trigger agent and        the detectable substance; and    -   an absorptive material which is porous, for absorbing the animal        excretion, the absorptive material comprising:        -   a water-absorbing polysaccharide providing absorptive            properties to the chromogenic absorbent material; and        -   a superabsorbent polymer (SAP).

In some implementations, there is provided the use of the chromogenicabsorbent material as chromogenic particles in combination with animallitter.

In some implementations, the animal litter comprises clay basedparticles, cellulosic particles, perlite based particles, silica basedparticles, corn based particles, paper based particles or wheat basedparticles or a combination thereof.

In some implementations, the clay based particles comprisemontmorillonite.

In some implementations, the clay based particles comprise bentonite.

In some implementations, the chromogenic absorbent material is used fordetecting blood in animal excretions.

In some implementations, the chromogenic absorbent material is used fordetecting glucose in animal excretions.

In some implementations, the chromogenic particles are substantiallyevenly distributed on a top surface of the animal litter.

In some implementations, the chromogenic particles are substantiallyevenly distributed within the animal litter.

In some implementations, the chromogenic particles comprise pellets,granules, disks, squares according to their process of manufacture.

In some implementations, there is provided a chromogenic absorbentmaterial for detecting a detectable substance in an animal excretion,the chromogenic absorbent material comprising:

-   -   a trigger agent;    -   a chromogenic indicator convertable into a colored and/or        fluorescent substance in the presence of the trigger agent and        the detectable substance; and    -   an absorptive material for absorbing the animal excretion, the        absorptive material having a porous and a block-shaped        microstructure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a scheme of the reaction pathway taking place in the particlesof chromogenic absorbent material for the detection of blood in animalexcretions.

FIG. 2 is a scheme of the reaction pathway taking place in the particlesof chromogenic absorbent material for the detection of glucose in animalexcretions.

FIG. 3A shows photographs of six samples of particles of chromogenicabsorbent materials after 30 minutes, 2 hours and 18 hours of contactwith a diluted blood solution.

FIG. 3B shows photographs of six samples of particles of chromogenicabsorbent materials including 1% of superabsorbent polymer after 30minutes, 2 hours and 18 hours of contact with a diluted blood solution.

FIG. 3C shows photographs of six samples of particles of chromogenicabsorbent materials including 2% of superabsorbent polymer after 30minutes, 2 hours and 18 hours of contact with a diluted blood solution.

FIG. 3D shows photographs of six samples of particles of chromogenicabsorbent materials including 3% of superabsorbent polymer after 30minutes, 2 hours and 18 hours of contact with a diluted blood solution.

FIG. 4 shows photographs of three samples of particles of chromogenicabsorbent materials including after 6 h 30 and 22 hours of contact witha diluted blood solution.

FIG. 5 shows photographs of samples of particles of chromogenicabsorbent materials including after 1 minute and 10 minutes of contactwith glucose solutions of different concentrations.

FIG. 6A is a ×200 scanning electron micrograph showing the surface of anextruded starch particle (comparative Figure).

FIG. 6B is a ×200 scanning electron micrograph showing the surface of anextruded starch particle in which gas was injected during extrusion(comparative figure).

FIG. 6C is a ×200 scanning electron micrograph showing the surface of aparticle of chromogenic absorbent material in which the absorptivematerial includes 50% PGS and 50% MCC.

FIG. 6D is a ×200 scanning electron micrograph showing the surface of aparticle of pressed cellulose (comparative figure).

FIG. 7A is a ×200 scanning electron micrograph showing a cross sectionof an extruded starch particle, obtained by freeze-fracture (comparativeFigure).

FIG. 7B is a ×200 scanning electron micrograph showing a cross sectionof an extruded starch particle in which gas was injected duringextrusion. The cross section is obtained by freeze-fracture (comparativefigure).

FIG. 7C is a ×200 scanning electron micrograph showing a cross sectionof a particle of chromogenic absorbent material in which the absorptivematerial includes 50% PGS and 50% MCC.

FIG. 8A is a ×400 scanning electron micrograph showing a cross sectionof an extruded starch particle, obtained by freeze-fracture (comparativeFigure).

FIG. 8B is a ×400 scanning electron micrograph showing a cross sectionof an extruded starch particle in which gas was injected duringextrusion. The cross section is obtained by freeze-fracture (comparativefigure).

FIG. 8C is a ×400 scanning electron micrograph showing a cross sectionof a particle of chromogenic absorbent material in which the absorptivematerial includes 50% PGS and 50% MCC.

FIG. 9 shows photographs of extruded starch particles (9A, comparative),extruded starch particles in which gas was injected during extrusion(9B, comparative), particles of chromogenic absorbent material in whichthe absorptive material includes 50% PGS and 50% MCC (9C), and particlesof pressed cellulose (9D, comparative).

DETAILED DESCRIPTION

A chromogenic absorbent material may include an oxidizing agent, achromogenic indicator and an absorptive material, for detecting diseasefeatures when contacted with animal excretions. In some implementations,the absorptive material includes a water-absorbing polysaccharide andoptionally a second crystalline polysaccharide and/or a superabsorbentpolymer, and may also have high-porosity and low-density properties.

In some implementations, the chromogenic absorbent material is providedfor detecting blood or glucose in excretions. More particularly, thechromogenic absorbent material may be used in connection with an animallitter. Processes for making chromogenic absorbent materials are alsodescribed.

It should be understood that excretion refers to any matter excreted byan animal, such as urine or fecal matter. The chromogenic absorbentmaterial may be used in any domestic animal litter including cat litter,dog litter and rodent litter. It may also be used for horse litter, cowlitter or any other livestock litter. However, various implementationsof the chromogenic absorbent material are not limited to detecting bloodor glucose in animal excretions and may be used to detect blood orglucose in human excretions, for example.

Particles of the chromogenic absorbent material may be dispersed withinthe animal litter or at the surface of the animal litter. The animallitter may include clay based particles, cellulosic particles, perlitebased particles, silica based particles, corn based particles, paperbased particles, wheat based particles or other organic-based litterparticles, or a combination thereof. For example and without beinglimitative, clay based particles may include bentonite and/ormontmorillonite.

In some implementations, the particles of chromogenic absorbent materialinclude: an oxidizing agent responsive to peroxidatic/pseudoperoxidaticactivity in an animal excretion to provide oxidizing activity, or afirst catalytic compound generating the oxidizing agent in situ; achromogenic indicator being chromogenically responsive to the oxidizingactivity of the oxidizing agent; and an absorptive material forabsorbing the animal excretion, the absorptive material including awater-absorbing polysaccharide providing absorptive properties to thechromogenic absorbent material.

In some implementations, the oxidizing agent and/or the first catalyticcompound, and the chromogenic indicator are distributed on at least anexterior surface of the absorptive material. In some implementations,the oxidizing agent and/or the first catalytic compound, and thechromogenic indicator are distributed within the absorptive material.

It should be understood that the expression “peroxidatic activity”refers to the ability of catalytic compounds to drive the reactionbetween hydroperoxides and colorless chromogenic electron donors whichbecome fluorescent or visibly colored after oxidation.

It should be understood that the expression “pseudoperoxidatic activity”refers to the ability of a peroxidase or a non-peroxidase catalyticcompound to drive the reaction between hydroperoxidases and colorlesschromogenic electron donors which become fluorescent or visibly coloredafter oxidation. Certain transition metals and their ions andhemoproteins are known to have pseudoperoxidatic activity. Basophils,neutrophils, eosinophils and mast cells synthesize endogenous peroxidasewhich can be visualized at the ultrastructural level in the secretoryapparatus of immature cells. Red blood cells and hematin containingcompounds have iron as part of their heme groups, which can catalyze theoxidation of chromogenic electron donors. This pseudoperoxidaticactivity can be inhibited with strong H₂O₂ solutions, sodium azide andmethanol-H₂O₂ solutions.

It should be understood that “particle” refers to any pellet, granule orpiece of various shapes. Optionally, the particles may generally have acircular cross-section with an average diameter ranging from 2.5 mm to10 mm. Optionally, the particles may generally have a square orrectangular cross-section with an average length ranging from 5 mm to 20mm. Optionally, the particles may have a top surface ranging from 19 mm²to 400 mm² and a thickness ranging from 1 to 10 mm. The shape(s) of theparticles may be conferred by their process of manufacture.

The oxidizing agent is reactive to peroxidatic/pseudoperoxidaticactivity and is able to oxidize the chromogenic indicator in thepresence of a peroxidase or a pseudoperoxidase. For example, theperoxidase can be horseradish peroxidase. For example, thepseudoperoxidase can be haemoglobin present in blood. In an optionalaspect, the oxidizing agent includes a hydroperoxide.

It should be understood that “hydroperoxide” refers to compounds of thegeneral formula ROOH, wherein the R group is an aryl, alkyl or acylgroup (organic hydroperoxide), or a hydrogen atom (hydrogen peroxide).For example and without being limitative, the hydroperoxide can becumehe hydroperoxide (CHP), diisopropylbenzene dihydroperoxide orhydrogen peroxide, or a mixture thereof. Hydroperoxides are suitable forthe detection of peroxidatic/pseudoperoxidatic activity.

In some implementations, the oxidizing agent may be a hydroperoxideprecursor such as sodium percarbonate. Sodium percarbonate is a chemicaladduct of sodium carbonate and hydrogen peroxide. The formula of sodiumpercarbonate is 2Na₂CO₃.3H₂O₂. Sodium percarbonate decomposes to sodiumcarbonate and hydrogen peroxide, for example upon contact with water.

In some implementations, the oxidizing agent is not initially added tothe chromogenic absorbent material, but is generated in situ by a firstcatalytic compound present in the chromogenic absorbent material. Itshould be understood that “generated in situ” means that the oxidizingagent is directly synthesized in the chromogenic absorbent material froma precursor. For example, the first catalytic compound may be an enzymesuch as an oxido-reductase. For example, the first catalytic compoundmay be glucose oxidase (GOx). Optionally, the precursor may be oxygen(O₂), which can be reduced to hydrogen peroxide in the presence ofglucose oxidase. In an optional aspect, the reduction of the precursorto the oxidizing agent can take place in the presence of a saccharide orpolysaccharide which can be oxidized by the first catalytic compound.

In some implementations, the oxidizing activity of the oxidizing agentis triggered by the presence of peroxidatic/pseudoperoxidatic activityin excretions. The oxidizing agent therefore oxidizes the chromogenicindicator which then changes of color. More particularly, thechromogenic indicator is an electron donor, i.e. a reducing agent thatchanges color upon losing an electron.

In some implementations, the chromogenic indicator is a benzidine-typecompound, i.e. a compound as shown in formula I:

In Formula I, groups R₁, R₂, R₃ and R₄ may be the same or different andmay be hydrogen, halogen, a lower alkyl or alkoxy group containing 1 to4 carbon atoms, a (C₁-C₄)-dialkylamino group, an acetylamino group, anitro group or an aromatic group which may be substituted.

Optionally, the chromogenic indicator may be a compound as shown inFormula II:

In Formula II, groups R₁, R₂, R₃ and R₄ may be the same or different andrepresent hydrogen, halogen, and a lower alkyl or alkoxy groupcontaining 1 to 4 carbon atoms, a (C₁-C₄)-dialkylamino group, anacetylamino group, a nitro group or an aromatic group which may besubstituted; R₅ and R₆ are the same or different and representwater-soluble groups as hydroxyl group, amino group, acidic group,disulfonyl group, ether group, halogen, and a lower alkyl or alkoxygroup containing 1 to 4 carbon atoms, a (C₁-C₄)-dialkylamino group, anacetylamino group or a nitro group.

Thus, a water soluble benzidine-type chromogenic indicator of FormulaII, responds in the presence of hydroperoxide and peroxidase by changingits light absorptive capability, which is due to the chemicaltransformation to the compound shown in Formula III:

It is understood that several different types of benzidine chromogenicindicators may be used.

Optionally, the chromogenic indicator may be3,3′,5,5′-tetramethylbenzidine (TMB). TMB is a colorless agent whichturns blue upon oxidation. The peroxidase and/or pseudo-peroxidasecatalyze the oxidation of TMB by the oxidizing agent (hydroperoxide)according to the following oxidation reaction.

The absorptive material includes a water-absorbing polysaccharideproviding absorptive properties to the chromogenic absorbent material.In some implementations, the water-absorbing polysaccharide may be astarch, a modified starch, amylopectin, amylose, modified amylose, acellulose derivative, a gelling polysaccharide or a mixture thereof.Non-limiting examples of starches and modified starches are starchgranules, pregelatinized starch, waxy starches, anionic starches,cationic starches, fractionated starches, cross-linked starches ormixtures thereof. Such starches may be obtained from many sources,including but not limited to wheat, maize, buckwheat, potato, cassaya,sorghum, millet, oat, arrowroot, barley, beans, peas, rice, rye, andmixtures thereof. Non-limiting examples of cellulose derivatives arecellulose esters and cellulose ethers, or a mixture thereof. Anon-limiting example of a cellulose ether is carboxymethyl cellulose(CMC). Non-limiting examples of gelling polysaccharides are agar-agar,guar and xanthan, or a mixture thereof.

Optionally, the water-absorbing polysaccharide can be a glass-likepolysaccharide. Glass-like polysaccharides are substantially amorphouspolysaccharides and include glass-like characteristics. Glass-likepolysaccharides substantially lack an organized crystalline pattern.Glass-like polysaccharides are typically prepared by melting or heatingthe polysaccharide to a temperature above its glass-transitiontemperature, followed by cooling to a temperature below its glasstransition or melting point temperature. A non-limiting example of aglass-like polysaccharide is pregelatinized starch.

Optionally, the absorptive material further includes a superabsorbentpolymer (SAP). Optionally, the absorptive material includes in weight upto about 3 wt. %, or between 1 wt. % and 2.5 wt. % of the SAP.Non-limiting examples of SAP are poly(acrylic acids) andpoly(methacrylic acids), salts thereof, or mixtures thereof. Anon-limiting example of SAP is sodium polyacrylate, which is anefficient SAP. It should be understood that other types of SAPs may beused, such as superabsorbent starches or other synthetic superabsorbentpolymers.

In an optional aspect, each particle of chromogenic absorbent materialfurther includes a second polysaccharide providing structural integrityto the chromogenic absorbent material. By “providing structuralintegrity”, it is meant that the second polysaccharide reduces orprevents the breaking up of the particles of chromogenic absorbentmaterial upon handling or upon contact with an animal excretion. Inother words, the second polysaccharide reduces the brittleness of thechromogenic absorbent material while preventing an increase of thesoftness or pliability of the chromogenic absorbent material. In somescenarios, the second polysaccharide provides sufficient structuralintegrity so that the particles of the chromogenic absorbent materialcannot be easily broken or fractured by hand and are relativelyunpliable and rigid solids.

For example, when the absorptive material consists of 100%pregelatinized starch, the particles of chromogenic absorbent materialcan tend to be soft and pliable and thus not as easily manipulated ordeposited onto animal litter without being damaged. Upon contact withanimal excretions, such pliable particles can still provide the desiredcolor change and activity, but can be more easily crushed, torn ordistorted by the animal.

Optionally, the second polysaccharide includes a crystallinepolysaccharide. Examples of crystalline polysaccharides are cellulose,cellulose derivatives or mixtures thereof. In an optional aspect, thecellulose includes microcrystalline cellulose (MCC) or nanocrystallinecellulose (NCC), or a mixture thereof. In an optional aspect, theabsorptive material includes in weight: about 35% to about 65%, or about45% to 55% of the water-absorbing polysaccharide; and about 35% to about65% or about 45% to about 55% of the second polysaccharide. In anoptional aspect, the crystalline polysaccharide is less water-absorbentthan the water-absorbing polysaccharide.

In some implementations, the chromogenic absorbent material may turnblue upon contact with excretions containing at least traces of blood(with therefore peroxidase/pseudo-peroxidase activity).

It should be understood that “blue” refers to any shade of blue. Thechromogenic absorbent material may need a contact time with excretionssufficient to enable coloration. In an optional aspect, the particlesmay turn blue after a contact time ranging from about 10 seconds toabout 30 min, or from about 10 seconds to about 1 min, depending on thenature of the absorptive material of the particles.

In some implementations, the chromogenic absorbent material may turn todifferent shades of blue depending on the blood or glucose concentrationin excretions. The intensity of the blue shade may be proportional tothe blood concentration or glucose concentration in excretions.

In some implementations, the chromogenic composition may further includea colour enhancer. Optionally, it may also include a buffering agent, astabilizer, a metal scavenger agent or a combination thereof. The colourenhancer may optionally be 6-methoxyquinoline, lepidin, phenolderivatives, nitrobenzene, N-methylpyrrolidone, ethylene carbonate orany combination thereof. The buffering agent may optionally includecitrate, sodium citrate, phosphate, acetate or any combination thereof.The stabilizer may optionally be ascorbic acid, ammonium molybdate andderivatives thereof, polyethylene glycol, polyvinylpyrrolidone,polyethylene oxide and derivatives thereof, or combination thereof. Themetal-scavenger agent may optionally be EDTA, EDTA sodium salt or anycombination thereof.

In some implementations, a chromogenic absorbent material is providedfor detecting a detectable substance in an animal excretion. Thechromogenic absorbent material includes:

-   -   a trigger agent responsive to the presence of the detectable        substance;    -   a chromogenic indicator convertable into a chromogenically        active substance in the presence of the trigger agent and the        detectable substance; and    -   an absorptive material for absorbing the animal excretion, the        absorptive material being porous and including:        -   a water-absorbing polysaccharide providing absorptive            properties to the chromogenic absorbent material; and        -   a second polysaccharide providing structural integrity to            the chromogenic absorbent material.

It is understood that the trigger agent may be selected depending on thedetectable substance and such that the conversion of the chromogenicindicator takes place and/or is catalyzed only if both the trigger agentand the detectable substance are present. For example, when thedetectable substance is a peroxidase or a pseudoperoxidase, the triggeragent may be an oxidizing agent responsive toperoxidatic/pseudoperoxidatic activity in the animal excretion and theconversion of the chromogenic indicator includes oxidation into thechromogenically active substance.

In some implementations, the detectable substance includes apseudoperoxidase (such as blood which includes haemoglobin), and thetrigger agent is a hydroperoxide (such as cumene hydroperoxide) or ahydroperoxide precursor.

In some implementations, the detectable substance is glucose, and thetrigger agent is a catalytic system including an oxido-reductase and aperoxidase, or an oxido-reductase and a pseudoperoxidase. For example,the oxido-reductase may be glucose oxidase and the peroxidase may behorseradish peroxidase.

In some implementations, depending on the absorptive material, theparticles of chromogenic absorbent material may have a density of about0.20 g/cm³ to about 0.39 g/cm³, of about 0.20 g/cm³ to about 0.35 g/cm³,of about 0.25 g/cm³ to about 0.35 g/cm³, or of about 0.30 g/cm³ to about0.35 g/cm³.

In some implementations, depending on the absorptive material, thechromogenic absorbent material may have a total porosity of about 65% toabout 85%, or of about 70% to about 80%. It is understood that the totalporosity refers to the fraction of the bulk material volume (V) which isnot occupied by solid matter. If the volume of solids is denoted by Vs,and the pore volume as Vpore=V−Vs, the total porosity can be expressedas shown in Equation 1 below.

$\begin{matrix}{{{total}\mspace{14mu}{porosity}} = {\phi = {\frac{V - {Vs}}{V} = {\frac{Vpore}{V}( {{mL}\text{/}{mL}} )}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

The total porosity may for example be measured by: placing a knownvolume of chromogenic absorbent particles into a container; covering theparticles with a liquid; and measuring the volume of liquid needed tocover the particles (Vc). The total porosity is then expressed as theratio of the volume of added liquid (Vc) to the volume of particles (V).

In some implementation, depending on the absorptive material, theparticles of chromogenic absorbent material have an effective porosityof about 0.5 mL/g to about 2.0 mL/g, of about 0.6 mL/g to about 1.5mL/g, of about 0.8 mL/g to about 1.2 mL/g or of about 0.9 mL/g to about1.1 mL/g. It is understood that the effective porosity (also referred toas connected porosity or true porosity) is defined as the ratio of theconnected pore volume to the total bulk volume. The effective porositymay for example be measured by: placing a known mass (m) of chromogenicabsorbent particles into a container; covering the particles with aliquid; measuring the volume of liquid needed to cover the particles(Vc); removing the soaked particles from the container; measuring theliquid remaining in the container (Vr); and calculating the volume ofliquid absorbed in the chromogenic absorbent particles (Va=Vc−Vr). Theeffective porosity may then be obtained as shown in Equation 2 below.

$\begin{matrix}{{{effective}\mspace{14mu}{porosity}} = {\phi_{e} = {\frac{{Vc} - {Vr}}{m} = {\frac{Va}{m}( {{ml}\text{/}g} )}}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

It is to be noted that the effective porosity may also be expressed asthe ratio Va/V in mL/mL.

In some implementations, the nature and form of the absorptive materialmay be selected and modified to allow sufficient internal diffusion andretention of excretions to facilitate the chromogenic indicator responseover time. For example, the absorptive material may be modified so as toincrease its porosity. The chromogenic indicator may also behomogeneously dispersed throughout the absorptive material according tothe preparation method of the chromogenic absorbent material. Thechromogenic indicator may be present not only at the exterior surface ofa given particle, but also in a neighboring sub-surface region that canbe rapidly exposed to excretions that are absorbed into the particle.

Additionally, when the absorptive material is glassy or substantiallytransparent, the presence of the chromogenic indicator in a sub-surfaceregion allows it to be readily visible when a color change occurs andalso avoids exposure to the air. In addition, the absorptive materialmay be provided with certain absorptive properties relative to theenvironment when in operation. For instance, the absorptive material maybe provided to enable faster absorption of excretions compared to thesurrounding material, such as surrounding animal litter, to facilitateadequate exposure of the excretions to the active agents in thechromogenic absorptive material. As different animal litters may havedifferent absorptive properties, the absorptive material may be providedin accordance with pre-determined litter absorption properties, e.g.according to a maximum litter absorption rate. For instance, in someimplementations, the absorptive material has a higher absorption ratecompared to the litter material, and optionally a substantially higherabsorption rate. For example, the absorptive material may have anabsorption rate about 3 to 10 times higher, or about 5 to 10 timeshigher than the absorption rate of the litter material.

In some implementations, the chromogenic absorbent material has a freeswelling capacity (FSC) greater than about 900%, or greater than about1000%. The FSC is one type of measurement used for measuring theabsorption properties of a material. An FSC measurement is performed bysoaking the material to be tested in a liquid to be absorbed (in thepresent case, water) for a given time and weighing the material afterthe liquid has been absorbed. In some implementations, the chromogenicabsorbent material has a higher FSC than compared to the littermaterial. For example, the chromogenic absorbent material may have a FSCabout 1.5 to 2 times higher than the FSC of the litter material.

Now referring to FIG. 9, a photograph showing different particles isshown. Particles 9A are extruded starch particles obtained under highshear, without injection of gas during extrusion. Particles 9A were madeas a comparative example. Particles 9B are extruded starch particlesobtained under high shear, with injection of gas during extrusion,Particles 9B were made as a comparative example. Particles 9D arepressed cellulose pulp particles and were also made as a comparativeexample. Particles 9C are chromogenic absorbent particles in which theabsorptive material includes 50% pregelatinized starch (PGS) and 50%microcrystalline cellulose (MCC). Particles 9C were obtained through aprocess as described below and correspond to sample 25 as detailed inExample 2.

As can be seen in FIG. 9, particles 9A and 9B are in the form of compactpellets and particles 9D are in the form of pressed, compact squares.Particles 9C of chromogenic absorbent material are in the form ofgranules having a concave shape on one side and a convex shape on anopposite side. Of course, it is understood that the particles ofchromogenic absorbent material may be of different shapes and bemanufactured as pellets, granules, disks or squares, according to theirprocess of manufacture.

Scanning electron micrographs of the particles of FIG. 9 were obtainedin order to compare the morphology of particles 9A, 9B, 9C and 9D.Scanning electron micrographs showing the surface of the particles areshown in FIGS. 6A to 6D. Scanning electron micrographs showing crosssections of the particles are shown in FIGS. 7A to 7C and 8A to 8C. Thescanning electron microscope used was a MEB JEOL JSM-5900LV™ (lowvacuum).

FIGS. 6A and 6B (comparative) show the surface of extruded starchparticles obtained under high shear, with and without injected gasduring extrusion. As can be seen, the surface of the extruded starchincludes microscopic starch globules having a size of between about 5 μmand about 30 μm.

FIG. 6D (comparative) shows the surface of pressed cellulose pulpparticles. Elongated cellulose fibers can be seen on the surface. Thefibers have a length of between about 100 μm and about 400 μm, and awidth of between about 10 μm to about 30 μm.

FIG. 6C shows the surface of chromogenic absorbent particles in whichthe absorptive material includes 50% pregelatinized starch (PGS) and 50%microcrystalline cellulose (MCC). Microsructures of various shapes canbe seen on the micrograph. The microsructures have a length of betweenabout 10 μm to about 100 μm, and a width of between about 10 μm to about100 μm.

Different microstructure morphologies are apparent for the differentparticles. The particles of FIGS. 6A and 6B mainly include a smoothglobular microstructure, the particles of FIG. 6D mainly includesgenerally smooth filamentous microstructure, while the particles of FIG.6C mainly include a rough, irregular, block-shaped microstructure.

The pore structure of the particles was also studied. Cross sections ofthe particles of chromogenic absorbent material were observed byscanning electron microscopy, as can be seen in FIG. 7C, and as detailedin Example 6. The cross sections were obtained by freeze-fracture underliquid nitrogen and observed by SEM to determine the pore density andequivalent diameter of the pores. It is understood that “pore density”refers to the proportion of the surface which is not covered by solidmaterial (i.e., the ratio of the pore surface to the total surface). Itis also understood that “equivalent diameter” refers to the approximatediameter of a comparable circular cylinder having the same volume asthat of the pore.

Depending of the absorptive material, the particles of chromogenicabsorbent material may have a pore density greater than about 20%, orgreater than about 25%, or of about 27% to about 33%, for example. Thepores of the particles of chromogenic absorbent material have anequivalent diameter greater than about 20 μm, or of about 20 μm to about40 μm, or of about 20 μm to about 30 μm.

Cross sections of extruded starch particles were also examined as acomparative example (see also Example 6), and can be seen in FIGS. 7Aand 7B.

Now referring to FIG. 1, an example of chromogenic absorbent materialfor detecting blood in animal excretions is described. The substance tobe detected (blood) includes haemoglobin which is a pseudoperoxidase. Inthe absence of blood (i.e., in the absence of peroxidase and/orpseudoperoxidase), the reduction of cumene hydroperoxide (the oxidizingagent) into reduction products and the oxidation of TMB into oxidizedTMB (oxTMB) is not catalyzed. When traces of blood are present (i.e.,when traces of haemoglobin are present), the reactions are enabled andTMB is oxidized into oxTMB which has a distinctive blue color. Thechromogenic absorbent material may be obtained to include a porouspolysaccharide matrix having a low density. Thus, the chromogenicabsorbent material described is suited for the detection of blood inanimal excretions, and therefore for detection of urinary tract diseasesfor example.

Now referring to FIG. 2, an example of the chromogenic absorbentmaterial for detecting glucose in animal excretions is described. Thechromogenic absorbent material used for detecting glucose includes afirst catalytic compound (such as glucose oxidase) to generate hydrogenperoxide in situ. In the case of glucose detection, the chromogenicabsorbent material further includes a second catalytic compound forcatalyzing the oxidation of TMB and the reduction of the hydroperoxide.The second catalytic compound may be horseradish peroxidase. It isunderstood that other peroxidases or pseudoperoxidases may be used inother implementations. It should also be understood that in the case ofglucose detection, the polysaccharide matrix does not includepolysaccharides which may react with the first catalytic compound. Ifsuch polysaccharides were used, hydrogen peroxide would be generated insitu even without the presence of glucose in the animal excretions,which would lead to false positive test results. For example, when thefirst catalytic compound is glucose oxidase, the absorptive materialdoes not include starches or modified starches that could react and givefalse positives.

Still referring to FIG. 2, when glucose is not present in the animalexcretions, TMB is not oxidized, as no hydrogen peroxide is generated insitu. When glucose is present in the animal excretions, glucose oxidaseoxidizes the glucose into gluconic acid and reduces oxygen into hydrogenperoxide. The horseradish peroxidase then reduces the hydrogen peroxideinto water and oxidizes TMB into oxTMB which has a distinctive bluecolor. The chromogenic absorbent material described in FIG. 2 may beobtained to include a porous polysaccharide matrix having a low density,and is suited for detection of glucose in animal excretions, andtherefore for detection of diabetes in animals for example.

In another aspect, a process of manufacturing particles of chromogenicabsorbent material is provided. In some implementations, the processincludes the steps of:

-   -   mixing together a water-absorbing polysaccharide, a second        polysaccharide and optionally an superabsorbent polymer, thereby        obtaining an absorptive powder mixture;    -   preparing a chromogenic solution by addition of a chromogenic        agent and an oxidizing agent or by addition of the chromogenic        agent and a first catalytic compound, into a solution;    -   combining the chromogenic solution with the absorptive powder        mixture so as to obtain solution-impregnated humid particles;        and    -   drying the solution-impregnated humid particles to obtain the        chromogenic absorbent material.

It is understood that the step of mixing may not performed in scenarioswhere the absorptive powder only includes one polysaccharide.

The chromogenic solution includes either the chromogenic agent and theoxidizing agent or the chromogenic agent and a first catalytic compoundfor generating the oxidizing agent in situ. In the case of chromogenicsolutions used for making particles of chromogenic absorbent materialfor the detection of glucose in animal excretions, the chromogenicsolution further includes a second catalytic compound which may includea peroxidase, a pseudoperoxidase, or a mixture thereof.

Optionally, the chromogenic solution may include a buffering agent so asto maintain a pH of the chromogenic solution between 5 and 7. Extreme pHmay be avoided.

Optionally, the chromogenic solution may include a colour enhancer, astabilizer, a metal-scavenger agent or a combination thereof as definedabove.

In an optional aspect, the chromogenic solution may be prepared andtailored to the particular absorptive material.

Optionally, the chromogenic solution may be combined with the absorptivematerial using a low-shear method. For example, the chromogenic solutionmay be combined with the absorptive material using a one-stepgranulation in a fluidized bed granulator. For example, the chromogenicsolution may also be poured onto the absorptive powder mixture to obtainthe solution-impregnated humid particles. In another example, thechromogenic solution may be poured onto the absorptive powder mixture toform the absorptive material, or dripped in the form of discrete dropsonto the absorptive powder mixture such that the drops are impregnatedwith respective amounts of the powder to obtain corresponding discretesolution-impregnated humid particles.

Optionally, the solution-impregnated humid particles may be recovered byfiltering the mixture of solution-impregnated humid particles andremaining absorptive powder through a sieve.

The drying step may be performed under vacuum and/or at varioustemperatures ranging from ambient temperature to about 65° C.

Using low-shear methods as described above allows for the manufacture ofparticles of chromogenic absorbent material having a lower density, ahigher porosity, different morphology, and enhanced absorptionproperties compared with other types of particles obtained by methodssuch as extrusion or pressing.

EXAMPLES Example 1

Experiments were performed by preparing particles of chromogenicabsorbent material having different compositions and testing theparticles when contacted with a blood-containing solution.

Particles of chromogenic absorbent material were prepared by mixingpregelatinized starch (PGS), microcrystalline cellulose (MCC) and sodiumpolyacrylate as the superabsorbent polymer (SAP), in powder form,thereby obtaining an absorptive powder mixture; pouring the chromogenicsolution on the absorptive powder mixture to obtain solution-impregnatedhumid particles; and drying the solution-impregnated humid particles inan oven at 65° C. to obtain the particles of chromogenic absorbentmaterial. In this case, the particles of chromogenic absorbent materialare in the form of granules having a length of between about 0.25 cm andabout 0.75 cm.

The chromogenic solution I that was used is detailed in Table 1:

TABLE 1 Molar mass Concentration Compound (g/mol) Mass or volume(mmol/L) Water (solvent) — 50 mL — Acetone (solvent) — 50 mL — TMB(chromogenic 240.34 312 mg  13 indicator) CHP (oxidizing 152.19 114 mg 7.5 agent) 4-lepidine (color 143.19 107 mg  7.5 enhancer)Polyvinylpyrrolidone — 30 mg — (stabilizer) Ascorbic acid 176.12 20 mg1.15 (stabilizer)

The particles of chromogenic absorbent material were prepared withvarying ratios of PGS/MCC and a varying amount of sodiumpolyacrylate-based SAP, and are numbered as shown in Table 2:

TABLE 2 0 wt. % 1 wt. % sodium sodium 2 wt. % sodium 3 wt. % sodiumpolyacrylate polyacrylate polyacrylate polyacrylate 35% PGS/ 1 2 3 4 65%MCC 40% PGS/ 5 6 7 8 60% MCC 45% PGS/ 9 10 11 12 55% MCC 55% PGS/ 13 1415 16 45% MCC 60% PGS/ 17 18 19 20 40% MCC 65% PGS/ 21 22 23 24 35% MCC

The particles of chromogenic absorbent material shown in Table 2 wereplaced on a bentonite-based litter and contacted with 5 mL of a 0.0215%blood solution or 5 mL of demineralized water which did not containblood. Particles which were not contacted with any solution were alsoplaced on the litter as a negative control.

FIGS. 3A, 3B, 3C and 3D illustrate samples as numbered in Table 2, andplaced on a bentonite-based litter. In each figure, the top pictureshows the granules 30 minutes after contact with the solutions, themiddle picture shows the granules 2 hours after contact, and the bottompicture shown the granules 18 hours after contact. In each picture ofeach Figure, the top row of granules is the negative control; the middlerow shows granules contacted with 5 mL of demineralized water which didnot contain blood; and the bottom row shows granules contacted with 5 mLof a 0.0215% blood solution.

As can be seen in FIG. 3A, granules No. 1, 5, 9, 13, 17 and 21 werecontacted with the different solutions (these granules contained 0 wt. %of superabsorbent polymer). The granules contacted with demineralizedwater did not change color and had the same white color as the negativecontrol granules 30 mins, 2 h and 18 h after contact. The granulescontacted with the blood solution had already turned blue 30 mins aftercontact. The blue coloration was distinctive. 2 h after contact, theblue coloration was still distinctive and present. 18 h after contact,the blue coloration had faded and the granules turned off-white oryellow. The blue coloration was present and distinctive for about 8hours before fading.

As can be seen in FIG. 3B, granules No. 2, 6, 10, 14, 18 and 22 werecontacted with the different solutions (these granules contained about 1wt. % of superabsorbent polymer). The granules contacted withdemineralized water did not change color and had the same white color asthe negative control granules 30 mins, 2 h and 18 h after contact. Thegranules contacted with the blood solution had already turned blue 30mins after contact. The blue coloration was distinctive. 2 h aftercontact, the blue coloration was still distinctive and present. 18 hafter contact, the blue coloration was still distinctive and present.The addition of 1 wt. % SAP had a positive effect on the retention ofblue coloration in the granules after contact with a blood solution.

As can be seen in FIG. 3C, granules No. 3, 7, 11, 15, 19 and 24 werecontacted with the different solutions (these granules contained about 2wt. % of superabsorbent polymer). The same results as the ones observedand illustrated in FIG. 3B were obtained.

As can be seen in FIG. 3D, granules No. 4, 8, 12, 16, 20 and 25 werecontacted with the different solutions (these granules contained about 3wt. % of superabsorbent polymer). The same results as the ones observedand illustrated in FIGS. 3B and 3C were obtained.

Example 2

Experiments were performed by preparing particles of chromogenicabsorbent material using different polysaccharides and mixtures thereof,and testing said particles when contacted with a blood-containingsolution. The polysaccharides used in this Example were pregelatinizedstarch (PGS), microcrystalline cellulose (MCC) andcarboxymethylcellulose (CMC).

The particles were prepared as described in Example 1. No superabsorbentpolymer was used in this Example and the mixing step was not performedwhen only one polysaccharide was used. The same chromogenic solution Ias described in Example 1 was also used.

Particles of chromogenic absorbent material were prepared using variouspolysaccharides and mixtures thereof, and are numbered as shown in Table3.

TABLE 3 Polysaccharide or polysaccharide mixture Sample number 50%PGS/50% MCC 25 100% CMC 26 100% PGS 27

FIG. 4 shows the granules 6 h 30 and 22 h after contact with 5 mL ofdemineralized water which did not contain blood (middle row) or 5 mL ofa 0.0215% blood solution (bottom row). The top row is the negativecontrol showing granules which were not contacted with either solution.A deep blue coloration rapidly appeared a few minutes after contact withthe blood-containing solution (not shown). The granules contacted withdemineralized water stayed substantially white or became slightlyyellow. After 6 h 30, samples No. 25 and 26 retained the deep bluecoloration, while the blue coloration of sample No. 27 was lighter.After 22 h, sample No. 25 retained the deep blue coloration, sample No.26 had a light blue coloration, and the coloration of sample No. 27 hadsubstantially faded.

It is to be noted that all the samples prepared enable the detection ofblood. Using 50% PGS/50% MCC as the absorptive material enabled the bluecoloration to be retained for a longer period when compared with 100%CMC and 100% PGS granules.

Example 3

Experiments have been performed by preparing particles of chromogenicabsorbent material using a mixture of 50% microcrystalline cellulose(MCC) and 50% carboxymethyl cellulose (CMC) as the absorptive material,and different chromogenic solutions. Said particles were contacted withglucose-containing solutions.

The composition of the chromogenic solution II is detailed in Table 4.

TABLE 4 Solvents and compounds Mass or volume Water (solvent) 50 mLAcetone (solvent) 50 mL TMB (chromogenic indicator) 312 mg  Glucoseoxidase (first catalytic  6 mg compound) Horseradish peroxidase  5 mg(second catalytic compound)

Chromogenic solution II shown in Table 4 was diluted at ratios of 1:2and 1:10 to obtain chromogenic solutions III (1:2 dilution) and IV (1:10dilution).

Particles of chromogenic absorbent material were prepared by mixingcarboxymethyl cellulose (CMC) and microcrystalline cellulose (MCC),thereby obtaining an absorptive powder mixture; pouring chromogenicsolution II, III or IV on the absorptive powder mixture to obtainsolution-impregnated humid particles; and drying thesolution-impregnated humid particles in an oven at 65° C. to obtain theparticles of chromogenic absorbent material. In this case, the particlesof chromogenic absorbent material were obtained in the form of granules.

FIG. 5 shows particles of chromogenic absorbent material 1 minute (toppicture) and 10 minutes (bottom picture) after contact with a solutioncontaining 0.03% of glucose. In each picture, the top row corresponds tochromogenic absorbent material made with chromogenic solution II, themiddle row corresponds to chromogenic absorbent material made withchromogenic solution III, and the bottom row corresponds to chromogenicabsorbent material made with chromogenic solution IV. As can be seen,when the more concentrated solution II was used, the blue coloration isdeeper and appears within 1 minute of contact. When the lowerconcentration solution IV is used, the deep blue coloration appearedwithin 10 minutes of contact.

Example 4

Experiments were also performed by measuring the free swelling capacity(FSC) of particles of chromogenic absorbent material. The particles ofchromogenic absorbent material were prepared as described in Example 1using PGS, Xanthan or guar as the water-absorbing polysaccharide, andMCC. The measurements were performed by soaking the samples in water for30 minutes and draining the water remaining at the surface for 10minutes. The values obtained were compared with the FSC values ofparticles obtained by extrusion or pressing. The results are detailed inTable 5.

TABLE 5 Particle type FSC % Extruded starch granule without gasinjection (comparative) 190 Extruded starch granule with gas injection(comparative) 200 Pressed paper pulp pellet (comparative) 500 50%PGS/50% MCC granule (sample No. 25 of Example 2) 1080 50% Xanthan/50%MCC granule 3360 50% guar gum/50% MCC granule 2030

The particles of chromogenic absorbent material made from PGS/MCC,xanthan/MCC and guar gum/MCC all exhibit high FSC values. This isindicative of a very high porosity and surprisingly high absorptionproperties when compared with the extruded starch granules and pressedpaper pulp pellets known in the art.

Example 5

Experiments have also been performed by measuring the density ofparticles of chromogenic absorbent material. The particles ofchromogenic absorbent material were prepared as described in Example 1using PGS, Xanthan or guar as the water-absorbing polysaccharide, andMCC. The values obtained were compared with the density values ofparticles known in the art and obtained by extrusion or pressing. Theresults are detailed in Table 6.

TABLE 6 Density Particle type (g/cm³) Extruded starch granule withoutgas injection (comparative) 0.60 Extruded starch granule with gasinjection (comparative) 0.48 Pressed paper pulp pellet (comparative)0.40 50% PGS/50% MCC granule (sample No. 25 of Example 2) 0.33 50%Xanthan/50% MCC granule 0.37 50% guar gum/50% MCC granule 0.26

The particles of chromogenic absorbent material made from PGS/MCC,xanthan/MCC and guar gum/MCC exhibit lower density values when comparedwith the extruded starch granules and pressed paper pulp pellets knownin the art.

Example 6

Experiments have been performed to obtain scanning electron micrographsof cross sections of particles of extruded starch with or withoutinjected gas during extrusion (FIGS. 7A and 7B, comparative) and of across section of a particle of chromogenic absorbent materialcorresponding to sample 25 as shown in Example 2 (FIG. 7C). The imagesobtained were analyzed to determine the pore density and the equivalentdiameter of the pores. Prior to imaging, the respective particles werefirst hardened by freezing in liquid nitrogen and cut in the frozenstate. The scanning electron microscope used was a MEB JEOL JSM-5900LV™(low vacuum).

The pore density and equivalent diameter measurements were performed byusing the Nikon NIS-Elements D™ image analysis software. The results aredetailed in Table 7.

TABLE 7 Equivalent Particle type Pore density (%) diameter (μm) Extrudedstarch granule without 7.6 7.8 gas injection (comparative) Extrudedstarch granule with gas 10.8 11.5 injection (comparative) 50% PGS/50%MCC granule 29.5 25.3 (sample No. 25 of Example 2)

The particles of corresponding to sample No. 25 of Example 2 have ahigher pore density and equivalent pore diameter than the particles ofextruded starch (made with or without gas injection during high shearextrusion).

Example 7

Experiments have been performed on sample No. 25 of Example 2 to measurethe total porosity and effective porosity of particles of chromogenicabsorbent material. Comparative measurements were also performed onextruded starch granules (with or without injected gas during high shearextrusion). The porosity measurements were performed as follows.

200 mL of particles were placed in a container. The particles wereweighed (mass m). Acetone was added to soak the particles and completelycover the particles with solvent. The volume of solvent required tocover all the particles was measured (Vc). The soaked particles wereremoved from the container and the volume of remaining solvent wasmeasured (Vr). The volume of liquid absorbed by the chromogenicabsorbent particles (Va =Vc−Vr) was calculated. The total porosity isthen obtained by calculating the ratio of the volume of added liquid(Vc) to the volume of particles (V), and the effective porosity iscalculated using Equation 2 detailed above. The results are summarizedin Table 8.

TABLE 8 Mass of Total Effective particles porosity porosity Particletype (g) Vc (mL) Va (mL) (%) (mL/g) Extruded starch 120 104 18 52% 0.15granule without gas injection (comparative) Extruded starch 96 116 1658% 0.167 granule with gas injection (comparative) 50% PGS/50% 66 150 6575% 0.985 MCC granule (sample No. 25 of Example 2)

As can be seen, the particles of chromogenic absorbent material made of50% PGS and 50% MCC have an effective porosity which is substantiallyhigher than extruded starch particles obtained with or without gasinjection during high shear extrusion.

The invention claimed is:
 1. A chromogenic absorbent material fordetecting glucose in an animal excretion, the chromogenic absorbentmaterial comprising: a first catalytic compound comprising anoxidoreductase, for catalyzing, in the presence of glucose, in situgeneration of an oxidizing agent responsive toperoxidatic/pseudoperoxidatic activity in the animal excretion; a secondcatalytic compound comprising a peroxidase, a pseudoperoxidase or amixture thereof; a chromogenic indicator oxidizable into a coloredand/or fluorescent substance in the presence of the oxidizing agent andthe second catalytic compound; and an absorptive material which isporous, for absorbing the animal excretion, the absorptive materialcomprising a water-absorbing polysaccharide, the water-absorbingpolysaccharide being unreactive to the first catalytic compound, whereinthe chromogenic absorbent material has a density of about 0.20 g/cm³ toabout 0.39 g/cm³ and an effective porosity of about 0.5 mL/g to about2.0 mL/g.
 2. The chromogenic absorbent material of claim 1, wherein thefirst catalytic compound comprises glucose oxidase (GOx).
 3. Thechromogenic absorbent material of claim 1, wherein the oxidizing agentgenerated in situ is hydrogen peroxide.
 4. The chromogenic absorbentmaterial of claim 1, wherein the second catalytic compound compriseshorseradish peroxidase (HRP).
 5. The chromogenic absorbent material ofclaim 1, wherein the first catalytic compound, the second catalyticcompound and the chromogenic indicator are distributed within theabsorptive material.
 6. The chromogenic absorbent material of claim 1,wherein the chromogenic indicator comprises a benzidine-type compound.7. The chromogenic absorbent material of claim 6, wherein thebenzidine-type compound comprises 3,3′,5,5′-tetramethylbenzidine.
 8. Thechromogenic absorbent material of claim 1, wherein the water-absorbingpolysaccharide comprises a cellulose derivative, a gellingpolysaccharide, or a mixture thereof.
 9. The chromogenic absorbentmaterial of claim 8, wherein the cellulose derivative is a celluloseester or a cellulose ether, or a mixture thereof.
 10. The chromogenicabsorbent material of claim 8, wherein the cellulose derivativecomprises carboxymethyl cellulose (CMC).
 11. The chromogenic absorbentmaterial of claim 8, wherein the gelling polysaccharide comprisesagar-agar, guar, xanthan, or a mixture thereof.
 12. The chromogenicabsorbent material of claim 1, wherein the absorptive material furthercomprises a crystalline polysaccharide.
 13. The chromogenic absorbentmaterial of claim 12, wherein the crystalline polysaccharide comprisesmicrocrystalline cellulose (MCC), nanocrystalline cellulose (NCC) or amixture thereof.
 14. The chromogenic absorbent material of claim 12,wherein the absorptive material comprises: about 35 wt. % to about 65wt. % of the water-absorbing polysaccharide; and about 35 wt. % to about65 wt. % of the crystalline polysaccharide.
 15. The chromogenicabsorbent material of claim 12, wherein the water-absorbingpolysaccharide is carboxymethyl cellulose (CMC) and the crystallinepolysaccharide is microcrystalline cellulose (MCC).
 16. The chromogenicabsorbent material of claim 1, wherein the absorptive material furthercomprises a superabsorbent polymer (SAP).
 17. The chromogenic absorbentmaterial of claim 1, wherein the chromogenic absorbent material isprovided with pores having an equivalent diameter greater than about 20μm.
 18. The chromogenic absorbent material of claim 1, having a freeswelling capacity greater than about 900%.
 19. The chromogenic absorbentmaterial of claim 1, wherein the density of the chromogenic absorbentmaterial is about 0.25 g/cm³ to about 0.35 g/cm³.
 20. The chromogenicabsorbent material of claim 1, wherein the effective porosity is ofabout 0.6 mL/g to about 1.5 mL/g.